Rotary trimmers which cut vegetation such as grass and weeds using flexible lines (flails) that project from a rapidly turning head are well known. Because the lines are routinely eroded or broken off in use, they must be replenished from time to time. It is undesirable to have to stop the trimmer to resupply the line or lines, although such a procedure is known in the prior art.
Improvements have been made which enable the line to be resupplied while the head continues to rotate. A very popular construction for this purpose is shown in Oberg U.S. Pat. Nos. 4,274,201 and 4,524,515 in which a downwardly projecting part of the head is pounded on the ground, and which by means of a serpentine arrangement feeds out a predetermined increment of line. This is the familiar "bumphead" device.
Another improvement that can enable line to be resupplied while the head continues to rotate is shown in Perdue U.S. Pat. No. 4,134,204. This device differs from Oberg in that the line can be resupplied without pounding the head on the ground. Instead, a manually operated linkage operates a release mechanism that enables line to be fed out as the consequence of lever or button movement. Many users of trimmers prefer this style of actuation.
It is an object of this invention to improve the latter style of actuation.
Every style of line trimmer has a handle-mounted rotary head. The head is manipulated by the handle, and a motive means is mounted to the handle to rotate the head. Motive means are such as electric motors or fractional horsepower gasoline engines. The type of motive means utilized is unimportant to this invention. The motive means can be mounted either adjacent to the head, which is conventional practice with electric motors, or at the other end of the handle from the head, which is conventional practice with gasoline engines. Placing the engine at the proximal end of the handle instead of at the distal end provides an improved balance for manipulation of the implement. This of course requires transmission means between the motor and the head, which is commonly provided as a flexible drive shaft, usually in the form of a wire or cable. This construction is in widespread usage.
Prior art constructions which release line as the consequence of an actuation other than impact with the ground utilize a separate system that actuates the release means, while the flexible drive shaft rotates the head. Thus, two systems are required.
It is an object of this invention to provide a simpler line feed mechanism which operates other than by impact with the ground, and which requires only one system for both head drive and line feed. The implement is thereby made simpler, lighter, and less expensive.
In addition, prior art line feeder heads are usually spring-loaded so that they return to a starting position at the end of each feed actuation. As a necessary consequence, line is then fed in two increments, which may be an excessive total feed-out. With this invention, only one increment need be fed, and a smaller feed-out per actuation can result.